在进度条的布局片段 [英] ProgressBar in Fragment Layout

问题描述

我无法访问我在onCreateView在片段的AsyncTask的创建片段的进度条。其造成的误差进度在preExecute是给NullPointerException异常。
我创建进度之前，我打电话的AsyncTask。所以，可能是什么问题？

 公共类HomeFragment扩展片段{    进度进度;    @覆盖
    公共查看onCreateView（LayoutInflater充气器，容器的ViewGroup，
            捆绑savedInstanceState）{        查看查看= inflater.inflate（R.layout.home_fragment，集装箱，FALSE）;        进度=（进度）view.findViewById（R.id.progressbar）;        新getAnnouncements（）执行（）;        返回视图。
    }    公共静态的newInstance HomeFragment（）{
        HomeFragment片段=新HomeFragment（）;        返回片段;
    }    私有类getAnnouncements扩展的AsyncTask＆LT;太虚，太虚，太虚＆GT; {        @覆盖
        在preExecute保护无效（）{
            super.on preExecute（）;
            progressBar.setVisibility（View.VISIBLE）;        }        @覆盖
        保护无效doInBackground（虚空...... PARAMS）{
            返回null;
        }        @覆盖
        保护无效onPostExecute（无效参数）{
            progressBar.setVisibility（View.GONE）;        }    }
}
 

home_fragment.xml

 ＆LT;进度
                    机器人：ID =@ + ID /进度
                    风格=机器人：ATTR / progressBarStyleLarge
                    机器人：layout_width =WRAP_CONTENT
                    机器人：layout_height =WRAP_CONTENT
                    机器人：layout_centerInParent =真
                    机器人：layout_marginTop =24dp
                    机器人：知名度=水涨船高/＆GT;
 

解决方案

 进度=（进度）view.findViewById（R.id.progressBar）;
 

I can't access the progress bar that I created in onCreateView of fragment in the Asynctask of fragment. Its caused by error is progressbar in onPreExecute is giving NullPointerException. I created progressBar before I call asynctask. So what might be the problem?

    public class HomeFragment extends Fragment {

    ProgressBar progressBar;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.home_fragment, container, false);

        progressBar = (ProgressBar) view.findViewById(R.id.progressbar);

        new getAnnouncements().execute();

        return view;
    }

    public static HomeFragment newInstance() {
        HomeFragment fragment = new HomeFragment();

        return fragment;
    }

    private class getAnnouncements extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            progressBar.setVisibility(View.VISIBLE);

        }

        @Override
        protected Void doInBackground(Void... params) {
            return null;
        }

        @Override
        protected void onPostExecute(Void args) {
            progressBar.setVisibility(View.GONE);

        }

    }
}

home_fragment.xml

 <ProgressBar
                    android:id="@+id/progressBar"
                    style="?android:attr/progressBarStyleLarge"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_centerInParent="true"
                    android:layout_marginTop="24dp"
                    android:visibility="gone" />

解决方案

progressBar = (ProgressBar) view.findViewById(R.id.progressBar);

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